Method of cold rolling steel strips and product thereof



May 29, 1934. J. A. sARGl-:NT 1,960,953

METHOD 0F COLD ROLLING -STEEL STRIPS AND PRODUCT THEREQF Filed March 17. 1932 lof@ Fly.

gwumtoz I Fly 8 JA. Sla/geni *gm @VM i UNITED STATES PATENT OFFICE RIETHOD F COLD .ROLLING STEEL STRIPS AND PRODUCT THEREOF y James A. Sargent, Sharon, Pa., assigner to Sharon Steel Hoop Company, Sharon, Pa., a corporation of Pennsylvania Application March 17, 1932, Serial No. 599,457

3 Claims. (Cl. 29-18) The invention relates to cold rolled steel strips strip steel may be satisfactorily and effectively and more Aparticularly to the manufacture of used as a base for receiving and retaining a vitpickled strip steel suitable for being used as a reous enamel coating, a lacquer coating, a paint material from which enamel Ware, galvanized coating, a galvanized coating, a plated coating,

5 products, plated and specially coated articlesfand or a non-ferrous metal coating, and the like. .6o

products provided with non-ferrous metal coat- I have discovered that cold rolled strip steel ings, may be satisfactorily made. having the above desired characteristics may be Difliculties are encountered in obtaining satisproduced by hot rolling Preferably thirty fOOt factory, complete and uniform adherence of a steel slabs into strips of any suitable gauge in vitreous enamel coating and the like to ordinary ,the usual manner and coiling the same; then 65 sheet or strip steel used in prevailing practice. C01d-r011ng the het felled StliDS t0 the desired Thus many pieces must be discarded as waste, gauge and ceiling the same; then box annealing following a burning operation in making vitreous the coiled cold rolled strips in either an oxidizenamel ware, because of imperfections which only ing or a reducing atmosphere; then passing the V become apparent after the pieces have been Strips through breaker rolls to break the coil 70 burned, due to unsatisfactory or non-uniform. set of the annealed material, to flatten and adherence between the enamel coating and the I straighten the strips, and to break up the hot sheet steel base. roll scale cold rolled into the surface of the Likewise, the life and efficiency of galvanized strips, Ol through COd red-Ging IOHS fOl the Same steel material, of non-ferrous metal coated steel purposes and t0 reduce the Strip thiCkIleSS; then 75 products, and of plated and specially coated steel coiling the Cold rolled Strips; then Continuously materials are dependent upon the efficiency or pickling the StliDS t0 emOVe the het T011 Settle uniformity of the bond between the surfacing or coating thereon and to produce cold rolled strips coating material andthe steel base therefor; with Toughened 01" pitted Surfaces; and then and diiculties are encountered in prevailing Ceiling the Seme t0 feeiitete Subsequent 112m- 80 practice, in obtaining' satisfactory adherence bedling, and t0 produce Cold felled StliDS in a Suittween such coating materials and the usual sheet ably coiled form adapted for use in carrying out or strip steel base. continuous stamping operations, and the like.

Steel sheets have sometimes been made for The hot rolled coiled strips are cold rolled r receiving enameled coatings by reducing and/or directly without pickling the hot rolled strips, 85 finishing the same on etched cold rolls, for pro- Vcontrary to universal practice, which requires hot ducing Toughened or pitted surfaces for the enrolled material to be pickled to remove hot roll gagement of the enamel coating material. Howscale before carrying out a cold rolling operation. ever, the cost of etchingcold rolls, and of main-` It has ordinarily been believed that unsound cold taining the same in a proper condition for aderolled products are produced if hot roll scale is 90 quately roughening or pitting the surfaces of cold not removed by pickling hot rolled products berolled material is so excessive that the cost of fore cold rolling the same. making cold rolled strips on etched cold rolls However, I have discovered that hot roll scale is practically prohibited. cold rolled into the surface of cold rolled strips 40 It is therefore an object of the present invenand then removed by a final pickling operation 95 tion to provide cold rolled strip steel during the forms roughened or pitted surfaces on the strips, process of making the same, with a uniformly so that the cold rolled pitted surface strips have Toughened or pitted surface, suitable for use in excellent characteristics for the adherence of obtaining complete, satisfactory and uniform adenamel, special or non-ferrous metal coatings,r

herence between the strip steel and enameled, and the like. u y 100 galvanized, plated, or nonferrous metal coatings The cold rolled coils may have any desired --applied thereto. weight up to the weight of a coil produced from It is a further object of the present invention to a thirty foot slab, the usual material from which provide strip steel suitable for use in making hot rolled strips are made; and stampings for .50 coated products without requiring unusual or exenamel ware and the like may be readily cut 105 pensive steps or operations to be carried out in from or punched in such coiled strips in aA conmaking the same. tinuous manner much more readily than the And finally itis an object of the present invensame are now being made' from sheet steel action to provide cold rolled strip. steel with a cording to prevailing practice, or sheets may be roughened or pitted surface at a low cost, which readily cut from the coiled strips for being gal- 110 vanized or for being coated with any desired non-ferrous metal coating, or the special coating may be applied in a continuous manner.

Furthermore, I have discovered that 'coiled strip steel cold rolled from hot rolled strips without pickling between the hot rolling and cold rolling steps, possesses all of the qualities and characteristics of cold rolled metal excepting only the surface finish, which in the present instance is roughened or pitted after the final pickling operation, and the economic production of a pitted surface cold rolled material is one of the desideratums of the present invention.

Accordingly, cold rolled strip steel made in accordance with the present invention can be used for any purposes which do not require cold rolled material to have smoothly finished or polished surfaces. Thus the improved strip ysteel may be used for receiving and retaining special coating materials; and the coating materials adhere much more tenaciously to the roughened or pitted surfaces of the same than similar coat-i ing materials adhere to ordinary sheet or strip steel manufactured in accordance with prevailing practice.

The presence of hot roll scale on hot'rolled strips, when the same are being cold rolled, irijures the ordinary steel cold rolls to such an extent as to practically prohibit their'use. Accordingly, special cold rolls must be provided, and I have discovered that hot roll scale coated strips may be successfully cold rolled by utilizing cast nickel-iron alloy rolls.

The improved method has been successfully carried out in the apparatus illustrated diagrammatically in the accompanying drawing in which Figure 1 is a diagrammatic view of a coil of hot rolled scale coated strip'steel;

Fig. 2 is a diagrammatic elevation of a continuous cold rolling mill;

Fig. 3 is a diagrammatic elevation of an annealing box and a box annealing furnace;

Fig. 4 is a diagrammatic elevation of a stand ofbreaker rolls and a coiler;

Fig. 5 is a vdiagrammatic view of a continuous pickling tank and coiler;

Fig. 6 is a diagrammatic view of -a coil of improved cold rolled strip steel;

Fig. 7 is an enlarged cross section through a hot roll scale coated cold roll strip prior to being passed through the pickling tank shown in Fig. 5; and

Fig. 8 is an enlarged cross section through the improved pitted surface cold rolled strip after being passed through the pickling tank, taken on the lin'e 8 8, Fig. 6.

Similar numerals refer to similar parts throughout the drawing.

In making the improved product by the improved method, steel slabs are hot rolled by single ply passes on roughing, edging and finishing mills to any suitable or desired gauge in the usual manner, and the hot rolled steel strips are then coiled to produce hot rolled strip steel coils indicated at 10 in Fig. 1. The hot roll scale which forms on both of the surfaces of the hot rolled strips 10 during the hot rolling operations is permitted to .remain on the surfaces of the strips, and the hot rolled steel strips 10 are not pickled.

Hot rolled steel strips 10 with hot roll scale thereon are then passed Without previously pickling, by single ply passes through a cold rolling mill indicated diagrammatically in Fig.'2, Which plurality of stands of cold rolls indicated generally at 11 and a coiler generally indicated at 12. The presence of the hot roll scale on the strips 10 as the same pass through the cold rolling mill requires the use of special hardened rolls in the cold roll stands 11; and it has been found that cast nickel-iron alloy rolls may be successfully used.

\ The hot roll scale on the hot rolled strips is cold rolled into the surfaces of the strips to form a cold rolled hot roll scale coating thereon as the strips pass through the cold rolls l1 and are coiled on the coiler 12 to form rolled steel strip coils 13.

A suitable number of coils 13 are then placed in tiers on the bottom 14 of a usual annealing box generally indicated at 15, and are covered by the usual annealing box cover 16. The annealing box is then pushed in the usual manner into the usual type of box annealing furnace 17, shown in Fig. 3, and the furnace may preferably include a plurality of chambers 18 which may be alternately charged.

The annealing furnace is brought to the desired temperature after which the box 15 is withdrawn from the furnace and allowed to cool. The annealing may be performed either in a reducing or oxidizing` atmosphere because the hot roll scale coating on the surfaces of the strip coils 13 may be reduced, or additional scale may be formed during the annealing step without affecting the characteristics of the ultimate product to be made, for the product is characterized by its roughened or pitted surfaces formed by cold rolling the hot roll scale into the steel strip.

The annealed coils 13 are then preferably passed through breaker rolls indicated diagrammatically at 19 in Fig; 4, for breaking the set of the coils, for flattening and straightening the strip', and for breaking the scale thereon to facilitate removal of the scale by the final pickling operation; or the annealed coils 13 may be passed through another cold reducing mill to further reduce the strip thickness.

In any event, the annealed cold rolled strips with hot roll scale coatings thereon are then coiled on a coiler indicated generally at 20 to form coils 21 which are then passed through continuous final pickling apparatus indicated generally at 22 in Fig. 5 and are coiled on a coiler 23 to produce the nished coiled pitted surface cold rolled steel product indicated generally at 24 in Figs. 5, 6 and 8.

An enlarged `section of the cold rolled strip 21 immediately before the same is passed through the pickling apparatus 22 is shown in Fig. 7 wherein the cold rolled strip steel 2lb is provided with surface coatings of hot roll scale 21a. Upon removal of the hot roll scale 21a by the final pickling operation, the pickle finished cold rolled strip 24 is provided with roughened, pitted or crater-like exposed surfaces 24a as shown in Fig. 8.

The pitted surfaces 24a of the cold rolled strip are caused by the cold rolling oi hot roll scale into the surfaces of the strip metal during the cold rolling operations; and the pitted surfaces provide very satisfactory means for obtaining uniform and complete adherence of enameled, galvanized, plated, or non-ferrous metal coatings or the like, subsequently applied to the pitted surface cold rolled steel strip.

The cold rolling of hot roll scale coated material breaks up the hot roll scale into small par- Ell@ is preferably a continuous type vmill including a'I ticles which are rolled into the metal to pit and 150 roughen the same, and the pits so formed have sharp, crag-like overhanging edges upon removal of the scale by the flnal pickling operation,

for the eil'lcient adherence of special coating materials.

It is not intended to limit the scope of the invention to the manufacture of a steel strip for any particular purpose because the improved pitted surface product made by cold rolling hot rolled steel strips without pickling the same to cause hot roll scale to pit the surfaces thereof, and then pickling the cold rolled strip, possesses all of the characteristics of full cold rolled strip steel excepting only a smooth surface, and the same may be used for any purpose which does not require the cold rolled strip steel to have a smooth surface; or may be used for deep drawing purposes because the pitted surfaces 'carry more lubricant into drawing dies than smooth surface material.

I claim:-

1. The method of making cold rolled steel strip with pitted pickle-finished surfaces for use as a. base for enamel coated products and the like, which includes the steps in the order named of hot rolling a strip by single ply passes to the desired gauge and uniformly forming hot roll scale throughout the surfaces thereof, cold rolling the strip without previously pickling by single ply passes to reduce the thickness of the strip and to cold roll the hot roll scale into` the surfaces of the strip whereby rough pitted surfaces are uniformly formed throughout the steel strip, and

finally pickling the strip to remove the cold rolled hot roll scaleand expose said rough pitted surfaces.

2. A cold rolled steel strip for use as a base I for enamel coated products and the like, said strip having substantially uniformly rough pitted pickle-finished surfaces, and said rough pitted surfaces comprising pits having sharp c rag-like 

